How long do some ozone-depleting molecules persist in the atmosphere before decaying?

• A. 10 to 20 years
• B. 25 to 30 years
• C. 50 to 150 years
• D. 200 to 300 years

Answer: (C)

Some ozone-depleting substances, particularly chlorofluorocarbons (CFCs) and other halogenated compounds, can persist in the atmosphere for an extended period, often ranging from 50 to 150 years. This longevity is due to their molecular stability, which makes them resistant to breakdown by atmospheric processes.

Because of this durability, these substances can travel to the stratosphere, where they release chlorine atoms through photolytic reactions when exposed to ultraviolet (UV) radiation. Each chlorine atom can destroy thousands of ozone molecules, contributing significantly to ozone layer depletion.

Understanding the persistence of these substances is crucial for assessing their environmental impact and the timeline needed for recovery of the ozone layer post-regulation. Thus, recognizing that many of these ozone-depleting molecules can remain in the atmosphere for several decades underscores the importance of international agreements like the Montreal Protocol, which aim to phase out the production and use of such substances.